Motion compensated inter-frame coding has been widely adopted in various coding standards, such as MPEG-1/2/4 and H.261/H.263/H.264/AVC. While motion-compensated inter-frame coding can effectively reduce bitrate for compressed video, intra mode coding is still required to process an initial picture or to periodically insert I-pictures (or Intra-coded picture, I-picture), and the I-pictures are inserted periodically to allow quick access to the compressed video data or to alleviate error propagation. Intra prediction exploits the spatial correlation within a picture or within a picture region. In order to further improve coding efficiency, the High-Efficiency Video Coding (HEVC) standard being developed exploits block-based spatial prediction extensively. In HEVC, multiple intra prediction modes are used to exploit spatial features and the number of intra prediction modes depends on the block size of a Prediction Unit (PU). For some PU block sizes (currently larger than 4×4), the number of intra luma prediction modes may be as many as 34. The intra luma prediction mode selected for each block has to be transmitted to the decoder side for proper decoding. The side information associated with the intra luma prediction mode may be substantial and therefore, it is desirable to develop schemes to improve the efficiency for coding intra luma prediction mode.
The intra luma prediction modes among neighboring blocks may be highly correlated. Therefore, the intra luma prediction modes from neighboring blocks that have been reconstructed may be used as a predictor for a current block. In HEVC, a coding scheme for the intra luma prediction mode is being considered, where the intra prediction mode of a current block is compared with the minimum of two intra luma prediction modes corresponding to two neighboring blocks. If the intra prediction mode of the current block is the same as the minimum of the two neighboring intra luma prediction modes, a single bit is transmitted to indicate the case. Otherwise, a single bit is transmitted along with information for the current intra prediction mode represented in fixed-length format. While the coding scheme for the intra luma prediction mode being considered may not fully exploit the correlations of the neighboring intra luma prediction modes, it is desirable to further improve the performance. Accordingly, a coding scheme that further exploits the dependency of the neighboring intra luma prediction mode is disclosed.